What stem cells are in the yolk sac?
There are several stem cells found after the development process of embryonic stem cells begins. The most studied of these cells are those that migrate to the bone marrow. These are the hematopoietic stem cells first detected in the yolk sac and the embryo from a stem cell referred to as the hemangioblast. The blood vessels needed by the hematopoietic stem cells are also formed from the hemangioblasts and are referred as the angioblast. The hematopoietic stem cells and angioblasts form the blood and immune systems of the fetus. Both stem cells remain in the body during and after birth, although at low levels. The angioblasts in the adult are renamed endothelial progenitor cells. These progenitor cells are capable of forming new blood vessels, as seen in the fetus.
